. Author manuscript; available in PMC: 2013 May 2.

Published in final edited form as: Thyroid. 2007 Apr;17(4):303–311. doi: 10.1089/thy.2006.0303

Table 2.

Mean Values for all Analytes in Pregnant and NonPregnant Subjects^*

	Nonpregnant	Pregnant
	Nonpregnant	1st trimester	2nd trimester	3rd trimester
Number of subjects	29	59	35	26
TT₄ LC/MS/MS (µg/dL)	7.12 ± 0.79	8.88 ± 2.67	10.67 ± 1.94^a	10.76 ± 2.00^a
FT₄ LC/MS/MS (ng/dL)	0.93 ± 0.25	1.13 ± 0.23	0.92 ± 0.30^a	0.86 ± 0.21^a ^b
FT₄ IA ng/dL	1.10 ± 0.25	1.05 ± 0.22	0.88 ± 0.17^a	0.89 ± 0.17^a
TSH (MU/L)	1.73 ± 1.13	1.13 ± 0.69	1.13 ± 0.54^c	1.04 ± 0.61^d

Values reported are mean ± standard error.

Significantly different from first trimester (p < 0.001).

Significantly different from second trimester (p < 0.001).

Not significantly different from first trimester.

Not significantly different from second trimester.

FT₄, free thyroxine; IA, immunoassay; LC/MS/MS, isotope dilution liquid chromatography tandem mass spectrometry; TSH, thyrotropin; TT₄, total thyroxine.